1. Field of the Invention
This invention relates to a retarder system for railway wagons of the kind comprising a track for railway wagons, a retarder device including a cylinder which is rotatable about its axis and is arranged substantially parallel to a rail of the track, and a helically extending flange, on the surface of the cylinder, provided with a wheel-contactable surface arranged to set the cylinder in rotation under the influence of a rail-engaging wheel of a wagon travelling along the track in a first direction. The rotational resistance of the cylinder then provides a braking action on the passing railway wagon. This rotational resistance can be accomplished by a hydraulic retarder built into the rotatable unit and operating by throttling the flow of a hydraulic medium, e.g. oil. The throttling may be speed dependent so that a braking action is only achieved at a certain speed, for example 3 m per second, of travel of the railway wagon. The system is particularly suitable for employment in marshalling yards.
2. Description of the Prior Art
Retarder systems of the kind referred to above are known as for example by U.S. Pat. No. 3,332,519 and Swedish Pat. Nos. 352,035 and 361,445. These known retarder systems are normally intended to retard railway wagons running in one direction only. To allow locomotives and, possibly other railway wagons to pass in a return or second direction opposite to the working or first direction, the known retarder systems may be provided with movable, e.g. pivotable, braking cylinder means. Typically, in a known retarder system provided with a pivotable cylinder means, the latter is pivotable between a working position and a pivoted position, and can be operated between these positions by hydraulic, pneumatic or electric operating members.
It is desirable for a locomotive or railway wagon to be able to pass the retarder device in the return direction when the cylinder is in its working position without any substantial retarding of the passing locomotive or railway wagon and without the risk of damage to the retarder device. This can be achieved by holding the brake cylinder in its working position in such a way that it is moved, e.g. pivoted, resiliently away from the rail when a flange of a passing rail-engaging wheel, during passage in the return direction, influences the helical flange of the brake cylinder. However, a problem in connection with the passage in the return direction has been to prevent the cylinder from being rotated about its axis from its normal position of readiness to an undesired angular position which reduces the braking capacity of the retarder device. One method of solving this problem is disclosed in Swedish Pat. No. 419,530. This patent discloses a fill portion at the rear side of the helical flange, i.e., the side opposite the contact surface thereof, to prevent the cylinder from being rotated about its axis from its normal position of readiness to an undesired angular position.
The aim of the present invention is to provide a retarder system in which a locomotive or railway wagon may pass the retarder device without a brake cylinder of the latter being moved out of its normal working position prior to the return passage of the locomotive or railway wagon. The brake cylinder is arranged so as to be moved resiliently from it normal working position under the influence of a flange of a passing rail-engaging wheel.